The API shows just how aggressive Instagram's growth has been, with the app adding roughly 5 million users every week. That explosive growth is primarily the result of the app's recent expansion to the Android platform and the app's acquisition by Facebook. Shortly after Facebook acquired Instagram, the app made its way to the top of the App Store charts for the first time since launch back in October 2010.

Instagram was released back on October 6, 2010, and the app reported 1 million registered users by December. In June of 2011, Instagram announced that their userbase had grown to 5 million users, and that number grew to 10 million in September of that year, closing the year around 15 million users. Since the Facebook acquisition, however, the app has passed 30 million users, and then 40 million users and, today, 50 million users.